The invention is directed to a cooling apparatus for cooling air of a blow-type extruder for a plastic material hose in which an annularly-shaped set of nozzles for the plastic material hose is connected to a plastic material supply device and is arranged coaxially to an internal air arrangement. The cooling apparatus comprises a cooling air nozzle ring is assigned coaxially to the set of nozzles and embracing the hose, with a blower supplying ambient air to the cooling air nozzle ring. The cooling apparatus is located in the conveyance path of the blower and is provided with a device for regulating the temperature of the cooling air to a set-up constant temperature in comparison with a measured temperature.
In a blow-type extruder for a plastic material hose a plastic material supply arrangement conveys liquified material to an annularly-shaped set of nozzles, which delivers the plastic material hose from an internal annularly closed slotted die, by hose with a horizontal arrangement of the set of nozzles or dies is conveyed away vertically. An internal- or auxiliary air arrangement is provided on the side of the set of nozzles facing away from the hose, which presses air into the hose in order to prevent same from collapsing or hold same in the expanded state. A pair of rollers is provided spaced from the set of nozzles or dies, which keep the hose closed at the end remote from the set of nozzles and conveys the hose away. The set of nozzles or dies is provided with a cooling air blowing ring at the side facing away from the internal air arrangement, from which air impinges upon the hose which leaves the slotted nozzle in the almost liquid state, in order to cool and solidify the hose material in an expeditious manner. The ambient air is for instance environmental air of a manufacturing hall or external air from outside of the manufacturing hall and is at a fluctuating and often too high a temperature. If this ambient air is blown for cooling purposes on the solidifying hose, then the finished hose comprises fluctuating and unstable properties along its length.
Because non-conditioned ambient air with a high and fluctuating temperature badly suits for cooling the hose, it can be envisaged to provide a cooling device with its own ventilator or fan which device itself aspirates and cools the ambient air. The blower aspirates the cooled ambient air. With such a proposal, the cooling device can be formed as a water-cooling device. A water-cooling device can not be controlled accurately to a specific temperature of the cooling air and permits only a minimum temperature of the cooling air of, for instance, 15.degree. C. Since the cooled air passes through the blower which produces heat, it should be cooled down to such an extent that it can absorb the heat produced in the the blower. In the proposal, the regulation can be accomplished as a function of the temperature of the air flowing towards the blower.